devtools.cleanup() disconnects other stores sharing the same connection

[chungyo]

Bug Description

When two stores share a Redux DevTools connection (the same name, with different store identifiers), calling devtools.cleanup() on one store disconnects the other store's DevTools subscription as well.

For example, create stores first and second with name: 'shared', then call first.devtools.cleanup(). A subsequent JUMP_TO_STATE message no longer updates second, even though that store is still in use. Separate connections are unaffected.

Expected: unsubscribe the cleaned-up store's listener, keep the shared connection working for the remaining stores, and close it when the last store is cleaned up.

Cause: the cleanup method calls connection.unsubscribe(), which removes all listeners on the connection. Meanwhile, the per-listener unsubscribe callback returned by connection.subscribe() is discarded. The two unsubscribe behaviors can be seen in the Redux DevTools implementation.

Investigated against Zustand main at b57db4f86ef179285da216eeb291266da82c361c. Related context: the cleanup API was introduced in #3111. This report concerns a surviving store on a shared connection.

Reproduction Link

Regression tests and extension test double — see the cleanup describe block. The test double models both per-listener unsubscribe and connection-wide unsubscribe.

To reproduce in a fresh clone:

git clone --branch fix/devtools-shared-connection-cleanup --single-branch https://github.com/chungyo/zustand.git zustand-cleanup-repro
cd zustand-cleanup-repro
pnpm install --frozen-lockfile
pnpm test:spec tests/devtools.test.tsx

# Keep the new tests, but restore the original middleware to reproduce the bug.
git show 245f5702070c0cba79386b18f7cdbff1dea1b4cf^:src/middleware/devtools.ts > src/middleware/devtools.ts
pnpm test:spec tests/devtools.test.tsx

The fixed version passes all 67 DevTools tests. With the original middleware, the three new regression cases fail: the remaining store does not receive the state update, and the shared connection is closed prematurely. These results were verified with a mocked extension connection; a live browser extension has not been tested.

Prepared Fix

Commit and diff

The patch retains and invokes the per-store unsubscribe callback, closes the shared connection only after its last store is removed, and makes repeated cleanup calls harmless. It includes regression coverage for surviving stores, repeated cleanup, and connection recreation.

Validation on the fixed version: all 227 tests pass, along with type checking, lint, formatting, and the package build. Implementation and verification were AI-assisted.

GitHub currently limits PR creation here to collaborators, so this is being shared through Discussions. Would a maintainer be willing to open a PR from this branch or apply the patch? If applying it directly, please retain the original commit authorship. Feedback on the proposed behavior is welcome.

[dai-shi]

Sounds valid. The patch looks a little bit complicated at a glance. I'll have a closer look later.

[dai-shi]

#3580 is open.